HPC-8748: Introduce project deleting util method

[Pl217]

With this PR, we're starting work on properly cleaning up related data upon deletion - HPC-8748. I was thinking of introducing a generic method wrapper for DB models, which would allow you to specify all tables with weak references to that model (table). I am using term "weak references" for tables which have objectId-objectType columns, which can have pointers to entities in other tables, without actual foreign keys. I have abandoned idea of a generic method for related data cleanup, because DB models would have to have reference outside tables, which goes against the separation of concerns and encapsulation.

Thus, I am introducing deletion utility methods. They will give us much more flexibility about setting deletion conditions and cleanup rules for each different table. The downside is that we need to remember to call the util method and not just model.destroy() on some tables.

To kickstart this idea of cleaning up properly after deletion, I have added utility method to delete a project and clean up afterwards. Along with that, I have added the possibility to delete just the latest version of the project - HPC-8746. We can already see that having utility method, rather than putting the logic into project.destroy() has advantages in allowing arbitrary complexity in logic.

Regarding project deletion, tables project and projectVersion have weak references in other tables:

• projectVersion:
  • categoryRef
• project:
  • budgetSegmentBreakdownEntity
  • flowObject
  • expiredData (table is still not used, but we should clean it up anyway)
  • authTarget

Table budgetSegmentBreakdownEntity has some records where objectType is "projectVersion". However, objectId values in these cases are actually pointing to project ID, not project version ID! Since this table is actually connected to project version by series of foreign keys, that means that deleting project also deletes budgetSegmentBreakdownEntity. That series of foreign keys is project->projectVersion->budgetSegment->budgetSegmentBreakdown->budgetSegmentBreakdownEntity